There is a technique of applying an LED as a light source of a backlight of a liquid crystal display device. The technique is directed to lower the power consumption by replacing a conventional cold-cathode tube with an LED.
Even in the case of using an LED as a light source, a light quantity loss occurs in a polarizer of a liquid crystal optical switch and a color filter. Consequently, the LED does not always have higher efficiency of use of light generated from the light source as compared with the cold-cathode tube, and reduction amount of power consumption is not so large.